The present invention relates to a structure of III-nitride light emitting diode (LED) and a manufacturing method thereof. More particularly, the present invention relates to the structure of III-nitride LED having spiral-shaped pattern electrodes, and the manufacturing method for making the same.
Nowadays, because LED has advantages of low manufacturing cost, low manufacturing difficulty level, easy and convenient installation and promising development future, LED is used widely in daily life, such as electronic bulletin boards, indicator lights and car taillights, etc. However, how to further enhance the irradiation efficiency of LED is still a target on which engineers are working.
FIG. 1 a illustrates a top view of a structure of conventional III-nitride LED, and FIG. 1b illustrates a cross-sectional view of a structure of conventional III-nitride LED along the A-Axe2x80x2 line in the FIG. 1a. Referring to FIG. 1a and FIG. 1b first, an epitaxial structure is formed by forming a buffer layer 14, a semiconductor layer 16 having a first electrical property, a confining layer 18 having the first electrical property, an active layer 20, a confining layer 22 having a second electrical property, and a contact layer 24 having the second electrical property in sequence on a substrate 12. Next, the aforementioned epitaxial structure is etched or polished to expose a portion of the semiconductor layer 16 having the first electrical property. Then, a transparent electrode 26 having the second electrical property, a metal electrode pad 30 having the second electrical property, and a metal electrode pad 28 having the first electrical property are formed on the epitaxial structure respectively, such as shown in FIG. 1a. 
The transparent electrode 26 having the second electrical property is used in the structure of the convention LED 10 to increase the current-spreading efficiency. In fact, most of the current 32 is concentrated within the shortest distance between the transparent electrode 26 having the second electrical property and the metal electrode pad 28 having the first electrical property, such as shown in FIG. 1b. Hence, the light-emitting area of LED 10 is mostly concentrated on the area on which the transparent electrode 26 having the second electrical property is close to the metal electrode pad 28 having the first electrical property, causing a poor light-emitting efficiency. Besides, due to the over-concentrated current, the temperature in local area is too high so that the life of conventional LED 10 is shortened. Although the prior art can increase the thickness of the transparent electrode 26 having the second electrical property to improve the current-spreading efficiency, yet as a result of that, the light permeability of the transparent electrode 26 having the second electrical property is reduced.
Further, in the conventional LED 10, if the photon produced from the light-emitting layer is ejected to the surface of diode with a large angle, it easily leads to the loss of total reflection, thereby reducing the extraction efficiency.
In view of the disadvantages of the conventional LED structure, the present invention provides a structure of III-nitride LED and a manufacturing method thereof to overcome the disadvantages of the conventional LED structure directly and effectively.
According to the present invention, the structure of III-nitride LED having spiral electrodes comprises: a substrate; an epitaxial structure located on the substrate, the epitaxial structure comprising a first stacked sub-structure located on the substrate, and a second stacked sub-structure formed in a spiral-shaped pattern on the first stacked structure, wherein the second stacked sub-structure has a trench exposing a side of the second stacked sub-structure and a portion of the surface of first stacked sub-structure; a first metal electrode having a first electrical property, wherein the first metal electrode having the first electrical property is in the trench and is located on the portion of the surface of first stacked sub-structure in the spiral-shaped pattern along the second stacked sub-structure, and the first metal electrode having the first electrical property is connected with a first metal electrode having the first electrical property pad having the first electrical property; and an ohmic electrode having a second electrical property, wherein the ohmic electrode is located on the second stacked sub-structure, and the second electrical property is opposite to the first electrical property, the ohmic electrode having the second electrical property comprising a transparent electrode having the second electrical property on the second stacked sub-structure, and a second metal electrode having the second electrical property, wherein the second metal electrode having the second electrical property is located on the transparent electrode having the second electrical property and the second metal electrode having the second electrical property is connected with a second metal electrode pad having the second electrical property. Further, according to the present invention, the method of manufacturing the structure of III-nitride LED having spiral electrodes is described as follows.
According to the present invention, the III-nitride LED having spiral electrodes can increase the current-spreading efficiency due to the spiral-shaped pattern of electrodes. Besides, if the photon is ejected to the diode surface with a large angle, the photon can be extracted from the side of the trench that is exposed by etching or polishing the spiral-shaped pattern, whereby the extraction efficiency of photon is increased.